1. Field of the Invention
The invention relates to a developing device for use in an image forming apparatus of the electrophotographic type, a process cartridge having the same, and an image forming apparatus having the process cartridge.
2. Description of Related Art
The construction of a process cartridge using a developing device according to the conventional art will be described below. In a photosensitive member unit of the process cartridge, there are disposed a photosensitive drum which is an image bearing member on which an electrostatic latent image is formed, charging means for uniformly charging the surface of a photoconductive layer of the photosensitive drum, and cleaning means for scraping off any residual toner not transferred to a recording medium but adhering to the photosensitive drum, and storing the scraped-off toner in a waste toner container.
Also, in a developing unit, there are disposed a toner container containing a toner therein, a developing roller for supplying the toner to the electrostatic latent image formed on the photosensitive drum and forming a visible image, a developing blade for giving triboelectrification charges to the toner and forming a toner layer on the surface of the developing roller, and a jet preventing sheet for preventing the leakage of the toner in the radial direction of the developing roller. The developing unit and the photosensitive member unit are rotatably connected together by an engagement pin. The engagement pin is provided at a location at which the developing roller supported by the developing unit and the photosensitive member supported by the photosensitive drum unit are movable. A biasing spring is provided between the developing unit and the photosensitive member unit so as to urge the developing roller toward the photosensitive drum.
In the above-described developing unit according to the conventional art, however, the developing unit and the photosensitive member unit are rotatably connected and therefore, the weight of the toner in the toner container is added to the pressure force urging the developing roller toward the photosensitive drum. Consequently, the pressure force pressing the developing roller toward the photosensitive drum fluctuates due to the consumption of the toner during image formation. The driving torque of the developing unit also fluctuates with the fluctuation of the pressure force.
It is an object of the present invention to provide a developing device in which the pressure force of a developing roller toward an image bearing member can be stabilized, a process cartridge having the developing device, and an image forming apparatus having the process cartridge.
It is another object of the present invention to provide a developing device in which the pressure force of a developing roller toward an image bearing member can be stabilized independently of the amount of developer in a developer containing portion, a process cartridge having the developing device, and an image forming apparatus having the process cartridge.
It is another object of the present invention to provide a developing device in which the pressure force of a developing roller toward an image bearing member can be stabilized and at the same time, an improvement in the assembling property has been realized, a process cartridge having the developing device, and an image forming apparatus having the process cartridge.
It is another object of the present invention to provide a developing device having:
a developing roller for developing an electrostatic latent image formed on an image bearing drum;
a developer containing portion for containing therein a developer to be supplied to the developing roller;
a first frame for supporting the developing roller;
a second frame for movably supporting the first frame, and supporting the developer containing portion; and
an urging member for urging the developing roller toward the image bearing drum,
a process cartridge having the developing device, and an image forming apparatus having the process cartridge.